Optical character recognition (OCR) technology of creating image data by scanning pages of notebooks and paper materials, etc., and recognizing characters in such documents by using this image data has been utilized. This technology enables the characters in the image to be converted into text (character codes), and thus, editing of the text or searching based on the text can be carried out easily.
Meanwhile, characters in the image may include characters of multiple languages (writing systems). When a character recognition process is performed for such an image, the image may not be able to be searched by a keyword (a character string) since characters of an unexpected language cannot be correctly recognized. Accordingly, it is necessary to realize a new function whereby an image including characters of multiple languages can be searched by a keyword.